Hell boys, we hear, alter appearance (8)

I believe the answer is:

disguise

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'appearance' is the definition.
(disguise is a kind of appearance)

'hell boys we hear' is the wordplay.
'hell' becomes 'dis' (term for the underworld in Greek myth).
'boys' becomes 'guys'.
'we hear' shows a homophone (sound like).
'guys' is a homophone of 'guise'.
'dis'+'guise'='DISGUISE'

'alter' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for disguise that I've seen before include "Conceal (one's identity)" , "front" , "Alter appearance to conceal identity" , "Altered appearance" , "Misrepresent; costume" .)

I've seen this clue in The Sun.

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